1. Field of the Invention
The present invention relates to power tools, and in particular to power tools such as hammer drills and impact drivers that have electric motors as drive sources.
2. Description of the Related Art
Known portable power tools typically have a motor accommodated within a housing and the motor generally includes a rotor, a stator and brushes. The rotor has a rotor shaft that is rotatably supported within the housing by means of bearings. The rotor includes an armature coil mounted on the rotor shaft. A commutator also is mounted on the rotor shaft on one side of the armature coil along the axial direction and is electrically connected to the armature coil. The stator is secured to the inner wall of the housing and may have a field coil that opposes the armature in the radial direction. The brushes are mounted on the inner wall of the housing by means of a brush holder and contact the commutator in the radial direction. The brushes are connected to a power source via a switch so as to supply electric current to the armature coil via the commutator. Such construction of the motor and the principle of rotation of the rotor are well known in the art; therefore, further explanation is not necessary. The rotation of the rotor shaft is transmitted to a spindle via a reduction gear mechanism. A drill bit, a socket, etc. can be mounted on the front end of the spindle.
The housing of known portable power tools is comprised of two housing halves that can be joined to each other to form the housing. This construction is advantageous to permit the motor and various parts to be inserted and assembled into the housing.
On the other hand, the brush holder is an integral member that has a substantially annular configuration so as to surround the commutator. The brushes are mounted on the brush holder in positions diametrically opposite of each other by means of brush supports, so that the brushes can electrically contact the commutator.
However, in the known power tools, because the brush holder is an integral member, it is not possible to assemble the rotor and the stator into the housing after the brush holder has been mounted within the housing. Moreover, it is not possible to assemble the brush holder into the housing after the rotor and the stator has been assembled into the housing.
Therefore, the rotor, the stator, and the brush holder of the known power tools must be assembled into the housing at one time, together with the associated reduction gear mechanism and other part. This assembling operation is very troublesome and time consuming, because the rotor must be inserted into the brush holder and must be held in this position prior to being set into the housing.
It is, accordingly, one object of the present invention to teach improved power tools, in which a rotor, a stator and a brush holder can be easily and rapidly assembled into a housing.
According to one aspect of the present teachings, power tools are taught that include a power tool housing comprising a plurality of housing segments arranged in the circumferential direction of a motor. The motor may preferably include a rotor, a stator and brushes. A brush holder may be disposed within the power tool housing, which brush holder is adapted to support the brushes. Preferably, the brush holder comprises a plurality of holder segments that are arranged in the circumferential direction of the motor.
Therefore, in order to assemble the motor into the housing, a first holder segment may be set into a first housing segment. The rotor and stator may be then set onto the first housing segment. Thereafter, a second holder segment may be joined to the first holder segment so as to form the brush holder that surrounds the rotor. Finally, a second housing segment may be joined to the first housing segment in order to form the power tool housing. Although two housing segments and two holder segments have been described, in fact, three or more housing segments and holder segments may be utilized with the present teachings.
Thus, the assembling operation of the rotor and the stator into the housing can be performed separately from the assembling operation of the brush holder. As a result, the assembling operation of the motor parts can be easily and efficiently performed.
According to another aspect of the present teachings, representative methods for assembling a motor into a power tool housing are also taught. As noted above, the power tool may comprise at least first and second housing segments, at least first and second holder segments and a motor having a rotor, a stator, and brushes. In this case, the first holder segment may be first set into the first housing segment. Preferably, the first housing segment is adapted to be joined the second housing segment in a circumferential direction with respect to the motor and thereby form the power tool housing. Moreover, the first holder segment preferably is adapted to be joined to the second housing segment in the circumferential direction of the motor and thereby form a brush holder that is adapted to hold the brushes.
Then, the rotor and the stator may be set into the first housing segment. The first holder segment may then be set into the second holder segment. At this time, the first and second holder segments may be fixedly attached. Thereafter, the second housing segment may be set onto the first housing segment and the first and second housing segments may be fixedly attached. Naturally, other methods for assembling the above-described housing segments, holder segments and motor may be utilized with the present teachings.
As noted above, the assembling operation of the rotor and the stator into the housing can be performed separately from the assembling operation of the brush holder. As a result, the assembling operation of the motor parts can be easily and efficiently performed.
These teachings may be used together or separately to make power tools of the present teachings. In addition, other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.